1. Field of Invention
The present invention generally relates valves and, in particular, to check valves that may be used to allow fluid to flow in one direction and prevent fluid from flowing in an opposite direction.
2. Description of Related Art
Conventional check valves are devices that allow gases, liquids or other fluids to flow in one direction. In particular, conventional check valves allow fluid to flow in a desired direction when sufficient pressure or force acts on the check valve. Conventional check valves, however, prevent fluid from flowing through the valve in an undesired direction. Specifically, when these pressures and forces are such that the flow of the fluid would be in the undesired direction, the check valve automatically closes resulting in the stopping or checking of the flow in this undesired direction.
Some known check valves use a flexible membrane that functions as a diaphragm. This diaphragm is designed to deform or bend in order to allow flow of fluid in a desired direction. This diaphragm may also return to its original position in order to prevent flow in the opposite direction.
Check valves have a positive pressure differential when there is greater pressure upstream from the check valve, in the desired direction of flow, than there is downstream from the check valve. In contrast, check valves have a negative pressure differential when there is greater pressure downstream from the check valve than there is upstream. If a positive pressure differential exists and it is sufficient in its magnitude, then the diaphragm may bend to create a space or passage through which fluid can flow through the check valve in the desired direction. The minimum pressure, or pressure differential, required to open a check valve is sometimes referred to as the cracking pressure. If no pressure differential or a negative pressure differential exists, or if a positive pressure differential exists but is insufficient in magnitude, then the diaphragm will prevent the flow of fluid through the check valve. In particular, the diaphragm will bend or deflect from its original or normal position to allow fluid to flow when there is a sufficient positive pressure differential. When there is no longer a sufficient positive pressure differential, then the diaphragm will return to its original or normal position to prevent flow though the valve.
Known check valves often have several shortcomings. For instance, some conventional check valves have a high cracking pressure. That is, these check valves require a large positive pressure differential before they will open. Disadvantageously, a check valve with an undesirably high cracking pressure will prevent flow in the desired direction even through the relative forces and pressures would normally allow this desired flow. Furthermore, some conventional check valves do not close until a relatively large negative pressure differential exists. A check valve that requires a substantial negative pressure differential to close may allow an undesirable or unacceptable amount of back flow, or flow contrary to the desired direction, when negative pressure differential of a small magnitude exists.
Additionally, some conventional check valves have components or structures that interfere with or resist the flow of fluid in the desired direction when the check valve is open. These known check valves that add resistance to the flow of fluid in the desired direction may undesirably decrease the efficiency of the system. Furthermore, some conventional check valves may leak when the valve is open, allowing some of the fluid to proceed or flow in a direction contrary to the desired direction.
Some conventional check valves may also produce noises as they open and close or when they leak. In some applications, the noise may be very undesirable and disconcerting. Furthermore, many known check valves are not aesthetically pleasing in their design. In addition, some known check valves have a large size and/or may be difficult to manufacture. For example, some conventional check valves may include components that have to be manufactured to relatively tight tolerances and interconnected in a very careful and meticulous manner.
Further, some conventional check valves have a complex design with a number of parts and components. Disadvantageously, the complex design may make the check valve more difficult and costly to manufacture. Conventional check valves with a complex design may also be more difficult to clean, maintain, repair and replace. Additionally, the complex design and numerous parts of some known check valves may be more prone to failure.